Field of the Invention
The invention relates to a novel method for initiating a gas generator in an air bag. More particularly the invention relates to a novel method of initiating a gas generator in an air bag from an external sensor.
Brief Description of the Prior Art
Gas generators for air bags are pressure vessels. One problem encountered in building gas generators with the sensor inside relates to the strength of the gas generator. The gas generator must be designed to contain more than a thousand pounds per square inch of pressure.
When the sensor is placed inside the gas generator, it is difficult to support the top and bottom of the gas generator except at the circumference. If the gas generator could be supported near its center then the thickness of the components would decrease and thus the weight of the entire inflator would be less.
The strength of the gas generator becomes even more critical when designing radial flow passenger side inflators which are typically at least twice the size of the driver side inflator. In designing passenger side inflators for compact and subcompact automobiles, space limitations preclude using inflators with increased length. Thus the diamters must be increased, and the top and bottom halves of the inflator must be made considerably stronger. As a result the inflator becomes significantly heavier and more expensive.
The latest concept in designing around this weight problem is to make the inflator in the form of a toroid and to place the sensor in the center of the toroid, outside the gas generator. The problem associated with this design is how to transmit the output from the sensor/initiator to the inflator.
Present toroid designs have shortcomings. They require a hole or passage for the output of the primer to initiate the gas generator which allows gas to escape from the inflator into the sensor housing. This requires the sensor housing to be constructed to withstand the pressures created by the inflator during operation.
Another toroidal design uses firing pins which impact stab primers which are embedded in the wall of the gas generator. This design also creates a hole in the inflator wall through which gases from the inflator can escape.